A rechargeable battery that is installed in a vehicle such as an electric vehicle (EV) or a plug in hybrid vehicle (PHV) serves as an electricity storage device that stores power supplied to a travel motor. The rechargeable battery may include an electrode assembly accommodated in a case. The electrode assembly includes sheets of positive electrodes and sheets of negative electrodes that are stacked insulated from one another. Each positive electrode includes positive active material layers applied to opposite surfaces of a positive metal foil. Each negative electrode includes negative active material layers applied to opposite surfaces of a negative metal foil.
In the case, tabs of the positive electrodes are electrically connected to a positive electrode terminal by a conductive member, and tabs of the negative electrodes are electrically connected to a negative electrode terminal by a conductive member. The positive electrode terminal and the negative electrode terminal partially extend through a wall of the case and project out of the case.
In a rechargeable battery such as a lithium-ion battery, the negative active material layers have a larger area than the positive active material layers, and each negative active material layer opposes the entire surface of the corresponding positive active material layer with a separator located in between. This reduces the deposition of lithium metal on the surface of the negative active material layer, which is caused by current concentration during charging.
In such a rechargeable battery, the negative active material layer opposes the vicinity of a basal portion of the positive electrode tab in a stacking direction of the electrode assembly with the separator located in between. Thus, when the positive electrode and the negative electrode are misaligned in a direction extending along a plane of the electrode assembly and the separator is displaced, the positive electrode tab and the negative active material layer may be short-circuited with each other. To limit short-circuiting of the positive electrode tab and the negative active material layer, one side of the separator is partially projected to form a guard that covers the vicinity of the basal portion of the tab (e.g., refer to patent document 1).